In a traffic control system, measurement quantities related to the traffic volume, etc. are collected from a lot of vehicle detectors installed in a road network, and based on the measurement quantities, traffic signals are controlled and traffic information to be provided to vehicle drivers is generated. Thus, the vehicle detectors play a core role in the traffic control system, and consequently, an abnormality (malfunction or operational abnormality) thereof can cause a significant decrease in the system performance. Therefore, it is desired to quickly detect an abnormality of the vehicle detectors.
JP5298712B2 discloses detecting an abnormality of the vehicle detectors by use of probe information (information on travel paths of vehicles) that is collected to generate traffic information to be provided to vehicle drivers.
Also, in the traffic control system, a traffic situation based on the measurement quantities of the vehicle detectors is displayed on a screen, and a user (such as a traffic manager and a road manager) conducts monitoring with this screen. In this monitoring, if the user is allowed to analyze the traffic situation and notice an abnormality of the traffic situation, namely, a state in which the traffic situation is significantly different from that in an ordinary time, the user will be able to make a decision regarding traffic guidance, traffic signal intervention, etc. properly.
JP4985825B2 discloses analyzing the control situation of traffic signals with a traffic signal control analysis device and displaying the analysis result on a display device.